The next type of opal we cut is crystal opal. Crystal opal is pure hydrated silica; it is translucent so you can see straight through it. It exhibits three of the things we look for when valuing an opal. We prefer the colour to be multi-directional, so you can see color from all different angles, the second thing we prefer is large blocks of color and the third thing is strong play of color that shows up in the dark.
The best way to test the play of colour of the opal is to give it the “miner’s test” by holding it out of the light in the shadows. Under the table is a good place because a real gem will still shine even though it is out of the direct light.